test 6

Question 1

why are kidneys so imporant

Answer 1

• Cells need a stable external environment if they are to perform at an optimum level.
• A stable external environment means the overall volume and composition of the body fluids must remain relatively constant
• The kidneys play a major role in maintaining the body fluids in terms of volume and composition

Question 2

Fluid intake

Answer 2

• [2300 mls/day]
   Synthesized by oxidation of carbohydrates (200 mls/day)
   Ingested fluids (2100 mls/day)

Question 3

Fluid loss / output

Answer 3

- [2300 mls/day]
 Insensible loss via respiratory tract and skin (not sweat) (700 mls/day)
 Sweat (100 mls/day)
 Feces (100 mls/day)
 Urine (1400 mls/day)

Question 4

Body Fluid Compartments (percent of body weight is water)

Answer 4

 Normal male: 60% of body weight
 Normal female: 50% of body weight (More fat)
 Tends to decrease with age

Question 5

Extracellular fluid

Answer 5

 20% of body weight
 1/3 of the total water volume
 Interstitial fluid (75% of ECFV)
 Plasma (25% of ECFV)
 Composition similar to interstitial fluid volume
 Transcellular fluid (1 to 2 liters) (pericardial, verebrospinal)

Question 6

Intracellular fluid

Answer 6

 40% of body weight
 2/3 of total water volume
 Composition of intracellular fluid very consistent across
different cell types (100 trillion cells)

Question 7

Gibbs-Donnan Equilibrium describes

Answer 7

 how ions are distributed on each side of a semi-permeable membrane when impermeable ions present on one side of the membrane (i.e. protein)

Question 8

Is the equilibrium appropriate based on these two rules

Answer 8

 Product of diffusible concentrations will be equal at equilibrium
 [6 Na(side1) x 6 Cl(side1)] = [12 Na(side2) x 3 Cl(side2)] = 36
 At equilibrium, the sum of all side 1 cations will equal the sum of all side 1anions AND the sum of all side 2 cations will equal the sum of all side 2 anions
 Side 1: 6 anions = 6 cations
 Side 2: 12 (3+9) anions = 12 cations

Question 9

what does this equilibrium produce :
Side 1: 6 Na, 6 Cl
Side 2: 12 Na, 3 Cl, 9 Protein

Answer 9

 Difference concentrations of ions on each side of the membrane without the need for pumping mechanisms
 Difference in osmolarity on each side of membrane

Question 10

Intracellular fluid ion concentrations

Answer 10

• KNOW THEM

Question 11

Nonelectrolytes of the plasma

Answer 11

• KNOW THEM

Question 12

Water distribution between plasma and interstitial compartments is controlled by what forces

Answer 12

 Capillary hydrostatic pressure (out)
 Interstitial hydrostatic pressure (usually out)
 Capillary colloid oncotic pressure (in)
 Interstitial colloid oncotic pressure (out)

Question 13

Water distribution between intracellular and extracellular

compartments is controlled by

Answer 13

 osmotic effect of sodium and chloride (mainly) across cell membranes
 Cell membranes:
 high permeability to water
 low permeability to solute
 Water moves quickly into or out of the cell to keep ICF isotonic with ECF

Question 14

Osmolarity of plasma, interstitial, and intracellular

Answer 14

 Osmolarity = osmoles / liter water
 1 osmole = 1 mole of particles (6.02 x 10^23)
 PLASMA: 301.8 mOsm/L (plasma protein)
 INTERSTITIAL: 300.8 mOsm/L
 INTRACELLULAR: 301.2 mOsm/L
-difference because of donnan effect of the proteins

Question 15

Osmotic Pressure

Answer 15

 Each mOsm of solute that cannot cross the membrane will generate an osmotic pressure of 19.3 mmHg
 Exposing RBC with intracellular osmolarity of 300 mmHg to pure water would result in an osmotic gradient across the cell membrane of 5790 mmHg
 MORAL OF THE STORY:
Small changes in the concentration of impermeable solute will create large shifts of water creating large changes in compartment volumes

Question 16

Isotonic solution

Answer 16

 Same osmolarity (i.e. same concentration of impermeant solutes) as cells
 Will not upset osmotic balance between intra and extracellular fluid when administered
 0.9% Sodium Chloride solution

Question 17

Isosmotic

Answer 17

Solutions with same osmolarity as intracellular osmolarity even if some solute is permeable

Question 18

Hypo-osmotic

Answer 18

Solutions with lower osmolarity than intracellular fluid even if some solute is permeable

Question 19

Hyperosmotic

Answer 19

Solutions with higher osmolarity than intracellular fluid even if some solute is permeable

Question 20

Osmotic Balance: Intra vs Extracellular

Answer 20

 Any difference in osmolarity is quickly corrected by transfer of water
 Response is very quick – within seconds
 Does take some time for equilibrium to be reached throughout entire body

Question 21

Causes of osmotic imbalance between intra and extracellular

Answer 21

 Water ingestion
 Dehydration
 Fluid loss from gastrointestinal tract
 Abnormal fluid loss by sweating or kidneys

Question 22

Adding Normal Saline

Answer 22

 Osmolarity of solution same as ECF
 No change in ECF osmolarity
 Expand volume of ECF by volume of solution
 Add 1 liter – the liter starts in the plasma of the CBV. Within 15 minutes 75% will move to the Interstitial fluid. 25% will remain in the CBV

Question 23

Adding Hypertonic solution

Answer 23

 Osmolarity of solution higher than osmolarity of ECF so ECF osmolarity will increase
 Osmolarity of ECF > than osmolarity of ICF so water moves from ICF to ECF
 Overall increase in osmolarity
 ECF volume increases (more than the volume added)
 ICF volume decreases
 Most of the sodium and chloride remains in the ECF

Question 24

Do math problems

Answer 24

• PRACTICE

Question 25

Adding Hypotonic solution

Answer 25

 Osmolarity of solution lower than osmolarity of ECF so ECF osmolarity will decrease  Osmolarity of ECF < than osmolarity of ICF so water moves from ECF to ICF  Overall decrease in osmolarity  ECF volume increases  ICF volume increases

Question 26

Adding isotonic solution

Answer 26

- ECV increases - No change in ICV - no change in overall osmolarity - Big change with the shift from the plasma of the circulating volume out into the interstitail volume

Question 27

Nutrient Solutions

Answer 27

 Glucose most common  All usually adjusted to (or nearly to) isotonic  If not, given slowly so does not upset balance  As nutrient metabolized patient often left with surplus of water  Usually removed via kidneys

Question 28

Plasma Sodium Concentration

Answer 28

 Good measure of plasma osmolarity  Sodium and chloride account for 90% of solute in ECF  Normal approximately 142 mE/L  Higher than normal: Hypernatremia – higher than normal osmolarity  Lower than normal: Hyponatremia – lower than normal osmolarity

Question 29

effect of Hyponatremia due to loss of sodium from ECF

Answer 29

 Decrease in plasma [Na+]  Decreased ECFV  Increased ICFV

Question 30

Causes of hypernatremia from loss of sodium

Answer 30

 Diarrhea & vomiting  Diuretic overuse (inhibit ability to conserve sodium)  Renal disease that “wastes” sodium  Addison’s disease results from decrease secretion of aldosterone

Question 31

effect of Hyponatremia due to addition of excess water to ECF

Answer 31

 Decrease in plasma [Na+]  Increased ECFV  Increased ICFV

Question 32

Causes of hypernatremia from excess water to ECF

Answer 32

 Excess water retention |  Excessive secretion of antidiuretic hormone

Question 33

Consequences of Hyponatremia

Answer 33

 Cell swelling – cerebral edema is major problem  Symptoms: headache; nausea; lethargy; disorientation  Significant problems as concentration falls into the 120 to 115 mE/L range  Significant brain swelling  Seizures  Coma  Permanent brain damage (if brain volume increases by more than 10%)  Death

Question 34

how does brain attempt to compensate during hyponatremia

Answer 34

 moving sodium, chloride, potassium, organic solutes from cells out to ECF  Have to be careful when treating not to correct too quickly [10 to 12 mmol/L over 24 hours]  Most common electrolyte disorder

Question 35

effect of Hypernatremia due to water loss from the ECF

Answer 35

 Increased plasma [Na+]  Decreased ECFV  Decreased ICFV

Question 36

Causes of Hypernatremia due to water loss from the ECF

Answer 36

 Inability to secrete antidiuretic hormone (needed for urine concentration) – produce large amounts of dilute urine (diabetes insipidus)  Excessive sweating so output greater than intake

Question 37

effect of Hypernatremia due additoin of excess sodium to ECF

Answer 37

 Increased plasma [Na+]  Increased ECFV  Decreased ICFV

Question 38

Causes of Hypernatremia due additoin of excess sodium to ECF

Answer 38

 Excessive secretion of aldosterone |  Reabsorb water and sodium

Question 39

Consequences of Hypernatremia

Answer 39

 Tissue cells shrink  Not as common as hyponatremia and requires very high sodium concentration (158 to 160 mEq/L) since high sodium concentrations result in intense thirst  Patient’s with hypothalamic disease have an impaired thirst reflex  Slow correction best

Question 40

Major causes of Intracellular Edema

Answer 40

 Hyponatremia  Depression of metabolic systems within cells  Sodium-potassium pump – shift of sodium into the cell  Lack of adequate nutrition delivery to cells  Inflammation  Increased cellular permeability – shift of sodium into cell

Question 41

Causes of Extracellular Edema

Answer 41

 Abnormal leakage of fluid from plasma to interstitial space across capillary  Most common form created by increased capillary filtration  Failure of lymphatics to return fluid from interstitial space to vascular system

Question 42

Causes of extracellular edema

Answer 42

Look at page 317